Field of the Invention
The present invention relates to a measuring apparatus, a measuring method, a lithography apparatus, and a method of manufacturing an article.
Description of the Related Art
Recently, as the micropatterning and integration of semiconductor devices such as ICs and LSIs advance, the accuracy and performance of a lithography apparatus such as an exposure apparatus are improving. As a lithography apparatus for manufacturing a semiconductor device, an exposure apparatus called a stepper or scanner is often used. In this exposure apparatus, a pattern of an original such as a mask or reticle is sequentially transferred to a plurality of portions (shot regions) of a substrate such as a wafer while the substrate is driven step by step. An exposure apparatus which performs this transfer at once is called a stepper, and an exposure apparatus which performs this transfer while scanning the substrate is called a scanner.
In the lithography apparatus, the accuracy of alignment between the original and substrate is an important element having a direct influence on the performance of the lithography apparatus. Therefore, a technique which aligns the pattern of the original and a pattern formed on the substrate on a nanometer order is required. The lithography apparatus is also required to improve the throughput (the number of substrates which can be processed within a unit time) from the viewpoint of the productivity.
As described above, the lithography apparatus is required to implement accurate alignment while improving the throughput. Therefore, a technique which measures an alignment mark on a substrate by using a sensor without stopping a stage holding the substrate is proposed in Japanese Patent Laid-Open No. 11-329943. Japanese Patent Laid-Open No. 11-329943 has disclosed a technique in which when an alignment mark has position information of one direction, (an image of) the alignment mark is measured by using a sensor while scanning the alignment mark in a direction perpendicular to the one direction. Since this technique can shorten the time (processing time) necessary to measure the alignment mark, it is possible to improve the throughput while implementing accurate alignment.
This related art is an effective technique when an alignment mark has position information in only one direction (for example, when elements of the alignment mark are arranged in only one direction). However, when an alignment mark has position information in two directions, the alignment mark must be measured after the substrate is stopped. Accordingly, this related art is sometimes unable to improve the throughput depending on the type of alignment mark.